dj,
While it is possible that the guy was jealous, I have had people do the same to me. But most often these people really don't understand why such shoes and why several balls may be necessary. Such people have had one ball all their lives, they bowl in one league at one house, just for the fun and for he social aspect. They truly don't get the idea of bowling in many different houses, on different approaches, in bowling tournaments, bowling on different oil amounts and patterns.
When such people come up to you and ask, I think you have to assume they really want to know for the sake of understanding, not because they're going to put you down for having a wide and varied assortment that they don't have.
I have also had some duffers come up to me and ask why I have so many balls. When I know them or are acquainted with them, I will often jokingly reply, "I am not as good as you; I need more options.", even though I may average 20 pins higher than they do. That is all in good fun. Then I explain the more serious side.